Antenna pointing apparatus



May 11, 1954 K. E. SCHREINER ANTENNA POINTING APPARATUS Filed Oct. 3. 1945 ATTORNEY Patented May 11, 1954 UNITED STATES PATENT OFFICE ANTENNA POINTING APPARATUS Kenneth E. Schreiner, Boston, Mass, assignor, by mesne assignments, to the United States of America as represented by the Secretary of War Application October 3, 1945, Serial No. 620,136

6 Claims. 1

This invention relates to highly directive ancausing an antenna to point in elevation at a selected target.

In many applications of radio object-locating apparatus it is desirable to point the antenna in elevation at a selected target. Antennas may be of two general types as classified by their elevation beam angles, narrow or broad. In general antennas having narrow elevation beam angles must be pointed directly at the selected target. This has previously been done by circuits utilizing signal strength of the echo returned by the target. The so-called cosecant squared (csc antenna is so designed that targets at all elevation angles produce substantially equal return signal intensities. However, such an anenna does not normally possess uniform azimuth resolution characteristics at all elevation angles. In applications wherein optimum azimuth resolution is desired elevation pointing is, therefore, desired. It will be obvious that other means than signal strength must be employed to properly point such an antenna because of its elevation characteristic mentioned above.

It is an object of the present invention, therefore, to provide a circuit for pointing an antenna in elevation.

For a better understanding of the invention,

together with other and further objects thereof, 9

reference is had to the following description taken in connection with the accompanying drawing which illustrates in block and diagrammatic form the preferred embodiment of the present invention.

Referring now to the drawing, there is shown the preferred embodiment of the present invention which comprises a control box II having voltages on leads l2, l 3 and I4, respectively designated VA, VG, and VREF. The control box H is preferably of the type disclosed and claimed in the copending application of Byron L. Havens and John J. Lentz, for Electrical Apparatus, Serial No. 620,135, filed October 3, 1945, but it may be any source providing an alternating voltage VA, which is proportional to the altitude of the aircraft or of the antenna, an alternating voltage Vc, which is proportional to ground range to the target, and a reference voltage Vase which is in phase with VG. is passed through a phase shifting device l which produces sufiicient phase shift in VA so that VA and VG are in 180 phase opposition. In the control box I I as disclosed in the cited copending application VA and Vc are in quadrature, and de- The voltage VA on lead l2 4 vice l5 then produces 90 phase shift. From the phase shifter l5, VA is impressed across a capacitor l6 and resisistor to ground. The voltage VG on lead I3 is connected across a potentiometer 2i. The potentiometer 21 is so constructed that the resistance to ground measured from the tap 22 when plotted as a function of displacement of the tap 22 is a tangent curve. The potentiometer 2| may alternatively be linear and so loaded, e. g. by resistor ii), that the output voltage will be substantially equal to a constant multiplied by the tangent of the angle by which the antenna 23 deviates from a predetermined position. The antenna 23 of the associated radio object-locating equipment is mechanically connected to the tap 22 in such a manner that the voltage on tap 22 will be proportional to the voltage, VG, multiplied by the tangent of the angle of depression of the antenna 23. Tap 22 is connected through a capacitor 24 and a resistor 25 to ground. The resistances of resistors l1 and 25 should be of equal magnitude. A resistor 26 and a resistor 21 are connected in series between the junction of capacitor I3 and resistor l1 and the junction of capacitor 2d and resistor 25. The resistances of resistors 26 and 27 should be equal. The junction of resistors 26 and 21 is connected to an amplifier 3| which in turn connects to a phase splitter 32. The phase splitter 32 may be any device capable of producing a push-pull output signal from a single-ended input signal. The pushpull output from the phase splitter 32 is connected to control grids 33 and 34 of multigrid tubes 35 and 36. Anodes 3? and 38 of tubes 35 and. 36 are returned to a suitable source of positive potential. The reference voltage VREF on line 14 which is in phase with VG is connected to a second grid 4! and 42, respectively, of tubes 35 and 35. A coil 43 of a differential relay denoted generally by 44 connects between cathodes 45 and 45 of tubes 35 and 36. A center tap on coil 43 is connected to ground. Fixed contact 5!, together with movable contacts 52 and 53 provide a singlepole double-throw switch which is connected to the motor which moves the antenna 23 in elevation. The elevation motor l0 and its associated power source 12 are connected as shown.

In the operation of the antenna elevation pointing circuit shown in the accompanying drawing an alternating voltage from control box I l of amplitude VA, proportional to the altitude of the aircraft, is properly shifted in phase and impressed across resistor l'l. At the same time an alternating voltage, VG, having an amplitude proportional to the ground range of the target, i. e.

an elementary consideration it will be seen that if the amplitude of the signals across iresistors l1 and 25 are equal no voltage will exist at the input to amplifier 3|.

at the input to amplifier 3i and will'have a Waveform such as 53 or 64, depending upon whether,

the antenna points too high or too low in elevatioin The signal at the input to amplifier 3| isamplified therein and-passed through the phase splitter 32-with resulting output Waveforms 65 and or 6'5 and 68, depending upon whether the input toamplifier 3! was as 63 or 64. The reference voltage VREF on lead :4 for control box II willhave a waveform and-phase indicated by II. If signals having phases indicated by 65 and 66 are present at'grids 33 and 34, it will be seen that tube-35 will conduct more heavily than will tube 36-with the result that contacts and 52 will make connection and the elevation motor will movetheantenna up in elevation to reduce the signal at theinput toamplifier 3i to zero. In an exactly similar manner it can be shown how the relay, M-Willbe operated to move the antenna down-in-elevation when the signal at the input to r-amplifler 3l-is as shown by Waveform 64.

While there has been described-What is at present 'eonsidered'the preferred embodiment of the invention; it will be obvious to those skilled in the art'that various changes and modifications may be made therein Without departing from the invention.

What is claimed is:

1.- An electrical apparatus associated with radio-object-locating equipment for pointing a rotatable antenna in elevation at a target, said apparatus comprising a signal source providing a pair of sinusoidal voltages proportional respectivelyto the altitude of the antenna above the target, and to ground range to the target, said source also providing a reference voltage, potentiometer means connected to said signal source and energized by said ground range voltage, said potentiometer means having a movable tap thereon mechanically connected to the antenna, phase shifter means connected to said signal source and providing from said altitude voltage an-output voltage substantially out of phase with the voltage'on said tap, resistive adding means connected to said phase shifter means and tap for providing a difference voltage proportional to the difference in magnitudes of the voltage on said tap and said output voltage, and comparator means operatively connected to said adding means and signal source for receiving said difference and reference voltages and being constructed and arranged and connected to said antenna for causing the antenna to rotate in such a direction asto reduce said diiferencevoltage to zero.

2. .-In antenna pointing apparatus of the character disclosed for use on aircraft for maintaining .an antenna pointing at a target, in combination, movable antenna means includingan Thisscondition is the de--"' sired condition, and the antenna 23. will point toward the target. However, ifvthe-antennadoesi not point toward the target, asignal willappear 4 antenna adapted to be selectively rotated in two opposite directions about a normally horizontal axis, means for obtaining a plurality of alternating voltage signals of the same frequency including a reference signal of predetermined amplitude, a ground range signal in phase with said reference signal and having an amplitude proportional tothe ground range-iof 'the target, and an altitude signal having a phase substantially degrees out of phase with said ground range signal, means energized by said ground range signal and operatively connected to said antenna for providinganoutput signal substantially proportional to 'ground range times the tangent of the angleofidepression'of the antenna from the true horizo'ntalymeans having said output signal and altitude signal applied thereto for providing a difference signal having an amplitude proportional .to the difference between the output and altitude signals and a phase determined by which of said last namedisignals is the'larger, and

meansoperatively connected to said last named means,-to said generator means, and to said antenna means for utilizing said difference signal.

and reference signal-to rotate said antenna r up and down selectively in accordance with the phase relation of said difference signalwith respect to said reference signal.

3. In antenna pointingapparatus of the character disclosed for use on aircraft for-main-- taining an antenna pointing at a target, in combination, movable antenna means including an antenna adapted to be selectively rotated in two.

opposite directions about a normally horizontal axis, generating means for obtaining three alternating voltage signals of the same frequency including a reference signal thaving a predetermined amplitude, a ground range signal in phasewith said reference signal and having'anamplitudeproportional to the groundrange of the target, and an altitudesignalhaving an amplitude proportional to the altitude of the aircraft and a phase difference of substantially ninety de-' grees with respect to said reference signal, phase shifter means connected to said generator means and having said altitude signal applied thereto for providing'a firstoutput signal substantially 180 degrees out of phase with said ground range signal, potentiometer means energized by said ground range signal and operatively connected to said antenna for providing a second output signal substantiallyproportional to ground range times the tangent of the angle of depression of the antenna from the true horizontal, adding network means having said first and second output-L signals applied thereto for providingea difference signal, and means operatively'connected to said? addinginetwork means, to said generator means, and to said antenna means for utilizing said difference signal and reference signal to rotate said" antenna up and down selectively in accordance" with the phase relation of said differencesignal with respect to said reference signal.

4." In antenna pointing apparatus of the char acter disclosed for use on aircraft for maintaining an antenna pointing at a target, in combination, movable 'antennameans including an antenna adapted tobe selectively rotated in two opposite directions about a normally'horizontal axis," means for obtaining a plurality of alternating voltage signals of the same frequency includinga reference signal of predetermined amplitude, a ground range signal in phase with said reference signal and having an amplitude proportional to the'ground rangeof the-target,-and

an altitude signal having a phase substantially 180 degrees out of phase with said ground range signal, means energized by said ground range signal and operatively connected to said antenna for providing an output signal substantially proportional to ground range times the tangent of the angle of depression of the antenna from the true horizontal, adding network means having said output signal and altitude signal applied thereto for providing a difference signal, phase splitter means operatively connected to said network means and energized therefrom for providing from said difference signal two additional difference signals of opposite phase and substantially equal amplitude, push-pull phase discriminator means energized by said two additional difference signals and having said reference signal applied thereto, and means energized from said phase discriminator means and operatively connected to said antenna for rotating said antenna.

5. In antenna pointing apparatus of the character disclosed for use on aircraft for maintaining an antenna pointing at a target, in combination, relay controlled movable antenna means including an antenna adapted to rotate in two opposite directions about a normally horizontal axis selectively in accordance with the contact position of the relay, generating means for obtaining three alternating voltage signals of the same frequency, including a reference signal having a predetermined amplitude, a ground range signal in phase with said reference signal and having an amplitude proportional to the ground range of the target, and an altitude signal having an amplitude proportional to the altitude of the aircraft and a phase difference of substantially ninety degrees with respect to said reference signal, phase shifter means connected to said generator means and having said altitude signal applied thereto for providing a first output signal substantially 180 degrees out of phase with said ground range signal, potentiometer means energized by said ground range signal and operatively connected to said antenna for providing a second output signal substantially proportional to ground range times the tangent of the angle of depression of the antenna from the true horizontal, adding network means having said first and second output signals applied thereto for providing a difference signal, phase splitter means operatively connected to said network means and energized therefrom for providing from said difference signal two additional difference signals of opposite phase and substantially equal amplitude, and push-pull phase discriminator means energized by said two additional difference signals and having said reference signal applied thereto, said phase discriminator means having said antenna control relay connected thereto and energized therefrom for causing said relay to assume two contact positions selectively in accordance with the phase relation between the reference signal and the difference signal.

6. In antenna pointing apparatus of the character disclosed for use on aircraft for maintaining an antenna pointing at a target, in combination, relay controlled movable antenna means including an antenna adapted to rotate in two opposite directions about a normally horizontal axis selectively in accordance with the contact position of the relay, generating means for obtaining three alternating voltage signals of the same frequency, including a reference signal having a predetermined amplitude, a ground range signal in phase with said reference signal and having an amplitude proportional to the ground range of the target, and an altitudesignal having an amplitude proportional to the altitude of the aircraft and a phase difierence of substantially ninety degrees with respect to said reference signal, phase shifter means connected to said generator means and having said altitude signal applied thereto for providing a first output signal substantially degrees out of phase with said ground range signal, potentiometer means energized by said ground range signal and operatively connected to said antenna for providing a second output signal substantially proportional to ground range times the tangent of the angle of depression of the antenna from the true horizontal, adding network means having said first and second output signals applied thereto for providing a difference signal, phase splitter means operatively connected to said network means and energized therefrom for providing from said difference signal two additional difference signals of opposite phase and substantially equal amplitude, electron discharge tube means including a pair of electron discharge tubes each having two grids, circuit means applying said two additional difference signals on one grid of each of said two tubes respectively, circuit means applying said reference signal in phase on the remaining grid of both of said tubes, said electron discharge tube means being connected to said relay for controlling the contact position thereof and causing said antenna to rotate in two directions selectively in accordance with the phase relation between the reference signal and the difference signal.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,407,275 Hays Sept. 10, 1946 2,410,666 Leck Nov. 5, 1946 2,412,003 Neufeld Dec. 3, 1946 2,412,612 Godet Dec. 17, 1946 2,414,108 Knowles Jan. 14, 1947 

